The present invention relates to a device for controlled penetration of the nail found on the hands and feet of a patient, and more particularly a device for the controlled penetration of the nail to aid in the treatment of infection of the nail such as for example the treatment for Onychomycosis commonly known as fungal nail. The device will penetrate the nail using a cutter advanced by a control system that will prevent the cutter from overrunning and entering the nail bed below.
Onychomycosis is an example of a fungal nail infection that is most common in the feet of the elderly affecting as many as 60% in the United States. It causes the nail to change shape, thicken and becoming brittle. Over the counter creams and ointments have a very low level of efficacy (of between 5-12%). Oral treatments are much more effective, however they must be taken for 2-3 months and can affect the liver making them contraindicated for some patients. An alternative means of treatment is the use of lasers to treat the infection, however the cost of the equipment and treatment is very high making it unavailable to many patients.
If untreated the nail can be permanently deformed and can have a significant impact upon the patient's quality of life due to the unsightly appearance of the nail and pain when wearing shoes.
To increase the local efficacy of topically applied treatment it is advantageous to deliver the treatment to areas within and below the nail. This greatly increases concentration levels that can be achieved in the nail bed and consequently improves efficacy of the treatment. The matrix is the tissue upon which the nail rests, the part of the nail bed that extends beneath the nail root and contains nerves, lymph and blood vessels. The matrix is responsible for the production of the cells that become the nail plate. The nail plate or body of nail is like hair and skin, made of translucent keratin protein made of amino acids. In the nail it forms a strong flexible material made of several layers of dead, flattened cells. If the nail is perforated then it allows antifungal treatment to be applied directly to the nail bed below the nail, where the infection resides. The challenge with drilling through the nail is to penetrate the nail without piercing the nail bed below. The nail bed is very sensitive and piercing it can cause the patient a lot of pain.
US patent application number 2006/0225757 A1 describes a drill for making a hole in the fingernail or toenail, however there is no provision for preventing the drill from overrunning into the nail bed, other than the skill of the user.
U.S. Pat. No. 6,264,628 B1 describes a device for cutting a notch in the nail. In order to prevent damage to the nail bed, the depth to which the notch is cut is predetermined prior to use. There is no method described for detecting the point at which the cutter breaks through the nail.
US patent application number 2011/0046626 A1 describes a method for drilling through the nail without drilling far into the nail bed. The author describes a method for detecting the point at which the drill breaks through the nail and into the nail bed below by measuring the electrical impedance of the tissue being drilled. The electrical impedance of the material being drilled is measured by using the drill as one electrode and having a second electrode placed on the skin of the patient. A change in impedance between the two electrodes may be used to detect the point at which the drill breaks through the nail and into the nail bed below. At this point however the drill may have progressed further into the nail bed than is desirable.
US patent application number 2010/0145373 A1 describes apparatus for drilling a hole in a nail of a subject. The Author describes a drill control unit configured to 2-60 back and forth motions per second. The apparatus is fed into the nail by the user and is dependent upon the user to ensure that it is not pressed too deeply into the nail bed. The Author describes a control unit configured to stop drilling in response to the force exceeding a threshold force, however the force will fluctuate according to the amount applied by the user.